Compensated key slot building construction



March 26, 1963 K. w. GRUBB 3,082,492

COMPENSATED KEY SLOT BUILDING CONSTRUCTION Filed Oct. 12, 1959 r ez T T) I v i I N 8 7 g INVENTOR.

N 3! fi'egrlz eilz Wayne firm 5* 1%. 1W

Unite This invention relates to building construction, and more particularly to building construction units particularly adapted to mass production for use in prefabricated house manufacture.

In the manufacture of modular or construction units to be utilized in the mass production of prefabricated houses, it is important that the various sections and subsections be so designed that they may be made and assembled at the site with a minimum amount of skilled labor. It is also important that such construction units be manufactured from conventional materials; that is, conventional both in dimensions and availability, so that maximum economy may be achieved. One difiiculty arises in the use of conventional or readily available material, such as wood, in the mass production of construction units as taught by the prior art; that is, the lack of any inexpensive means for eliminating the effect of variations in the dimensions of ordinary building lumber as it is received from the mill.

It is as object of this invention to provide an improved construction unit capable of mass manufacture from readily available building material, in which variations in the dimensions of the building material are compensated for without the necessity of expensive operations upon the material.

It is a further object of this invention to provide a construction unit capable of mass manufacture for use in prefabricated houses, in which all nailing of joints in the unit may be eliminated, and in which all elements that make up the construction unit are precut to predetermined dimensions.

It is still another object of this invention to provide a wood construction unit capable of mass manufacture for use in prefabricated houses, in which the elements making up the construction unit are precut to modular lengths and joined in such manner that the overall dimensions of each of the construction units will be held to exact values regardless of the variations in dimensions of the wood elements as to nominal widths or thicknesses.

It is most important that construction units of the massproduced type be kept within certain predetermined dimensions, regardless of variations which may be encountered in the thicknesses of stock lumber. Normally available lumber as utilized in the building of houses, such as 2 by 4s, 2 by 6s, 2 by 8s and so on, all varies in some degree from the stated dimensions. For example, a 2 x 4 piece of lumber is usually supposed to be 1%" thick by 3%" wide, but in actual practice these dimensions may vary in extreme cases as much as A3". The assembly of construction units according to this invention compensates for such variations in the dimensions of the elements making up the construction unit.

The carrying out of this invention contemplates the use of interlocking joints between elements making up the construction unit, to eliminate much of the necessity for nailing the elements together. The interlocking joint is of a special type which compensates for variations from standard in the dimensions of the elements making up the construction unit. This interlocking joint, which is to be described in detail later in the specification, and termed a compensated key-slot joint of the dovetail variety, is

States atcnt 3-,fi8ZA9Z Patented Mar. 26, 1963 the means by which the construction unit elements, cut to predetermined lengths, are assembled to form the construction units themselves that are capable of interchangeable assembly, because all variations from standard dimensions of the elements have been compensated.

The invention will be described as it applies to specific construction units, such as wall frames utilized in house construction, but it will be obvious that the invention is applicable equally well to other types of frames utilized in house construction, as well as to other frames utilizing precut elements in many other fields of construction.

For a more detailed description of the invention, refcrence is made to the following specification, to be read in conjunction with the attached drawings, in which:

FIGURE 1 is an elevational view of a pair of wall frame construction units made in accordance with this invention.

FIGURE 2 is a detailed view in perspective of a dovetail joint with the compensated key slot construction as used in the wall frame units illustrated in FIGURE 1.

FIGURE 3 is a perspective view of a known dovetail joint shown as employed in the stretcher portions of these prefabricated building elements.

FIGURE 4 illustrates in perspective a compensated key slot joint for use in main horizontal elements to compensate for variations in the original dimensions of the material.

Referring to FIGURE 1 of the drawings, the reference numeral 10 designates a typical wall section of a house that is constructed of 2" x 4" lumber elements in accordance with this invention. The wall section 10 includes a subsection shown at the left, and an adjoining wall section shown at the right, both formed of a plurality of vertical studs 11, and top and bottom plates 12 and 13 respectively. The wall section may also include the requisite number of stretchers 14, a door opening 15 in one subsection, and a window opening 16 in the other subsection.

In the construction of wall units such as are illustrated in FIGURE 1, it is necessary that the vertical dimension A and the horizontal dimension L of the contemplated frames be kept within certain predetermined limits, or such units cannot be used interchangeably in prefabricated housing. For economy of manufacture it is necessary that each of the elements used in the wall frame =10 be precut to a desired dimension of length and then assembled by means of dovetail joints to form a finished product that is uniform in its outside dimensions L and A, so that each wall frame thus produced will have the same dimensions within predetermined limits.

However, the lumber readily available from ordinary commercial sources varies to some degree from the Width and thickness dimensions for which it is sold. As stated previously, a 2 x 4 piece of lumber may vary in thickness by as much as /3 from its nominal standard dimensions of 1 /8" in thickness and 3%" in width. In regular building work such variations in dimensions can be tolerated, being adjusted by the carpenters, but in prefabricated house construction work, all construction units must not only fit properly, but all units of the same type must be interchangeable, so that there will be no difliculty in final assembly of each housing unit.

In order to compensate for variations in the width and thickness dimensions of the elements that form the unit, the elements are joined in a manner which compensates for such variations in dimensions. FIGURE 2 illustrates in detail the manner in which two of the elements are joined in a compensated key-slot dovetail joint that will compensate for the dimensional variations just mentioned. In FIGURE 2 the vertical stud 11 is fitted to the bottom plate member 13 by means of a dovetail joint having a compenasted key slot. The dovetail joint is formed by the usual wedge shaped slot or groove 17 in the bottom plate 13 to receive the male wedge or tongue portion 18 cut to shape on the end of the stud member 11. The slot in the bottom plate 13 is cut to such a depth that the dimension B is always a constant, while the dimension D will vary depending upon the actual thickness of the lumber used for the top plate 12 and the bottom plate 13. The dimension D, therefore, which represents the compensation feature of the key-slot, will be varied according to the actual dimensions of the lumber used in the two elements 12 and 13 that are being joined by the third element 11. The upper end of each stud 11 is, of'course, fitted in an identical manner to the top plate 12 when the frame is assembled. The studs 11 can be accurately cut to the necessary length, as for example, if a Wall frame unit were desired having the A dimension of 8 feet, the constant dimension B representing the dovetail position from the outer face of the member 13 would be held to 1 inch (say), so that the studs 11 would all be cut to a total over-all length of 7'10.

The compensation type of joint just described cannot be utilized cumulatively unless two compensated key slot joints are placed back to back as illustrated at 19 in FIGURE 1. Although it is not necessary to compensate horizontally in the direction of the stretchers 14, the total length L of the wall section 10 can be maintained accurately by the use of back to back compensated keyslot joints at each subsection, as for example at the junctures 19 and 20 and corners 23 where the compensated key-slot joint illustrated in detail in FIGURE 4 would be used. In forming the dovetail slot on the side of the stud member 11, the bottom of the slot is always maintained a fixed distance E from the outer face 20 of the stud 11, While the depth F of the compensated key-slot 21 will vary in accordance with the variations in thickness of the stud 11. Thus by placing two such compensated key-slot joints back to back as shown in FIGURE 1, and with compensated key-slot joints at the subsection upper and lower ends, it is possible to maintain the total dimension L substantially constant.

The stretchers 14 can be joined to the studs 11 by conventional dovetail joints as illustrated in FIGURE 3, there usually being no necessity of compensation for these members.

The female or groove portion of the compensated keyslot joint thus comprises an ordinary dovetail groove which, instead of intersecting the face of the lumber at its inclined faces, intersects this face via an intervening rectangular cut of suitable depth and of width adequate to receive the end of the connected element. The adjustment for variation in dimensions is made in this straightsided transition portion without disturbing the final dovetail relationship desired.

Although the invention has been described and illustrated as used in a particular type of construction or building unit, it is obvious that the compensated key-slot type of joint may be used in all situations where it is desired to join a pair of building elements by a third element in such manner that the variations in element dimensions may be compensated for to give a resultant unit that maintains outside dimensions within predetermined limits.

What is claimed is:

l. A structural assembly having a dimension defined as the distance between first and second spaced parallel planes and comprising first and second structural members which exhibit unavoidable variances as to stock thickness between opposite surfaces thereof; said members being. disposed in parallel relation with the outer surface of each lying in a respective said plane; a plurality of oppositely disposed pairs of dovetail slots inside the inner surfaces of said structural members, each said slot having side walls converging toward the respective said inner surface and a bottom Wall, with each said bottom wall spaced a precisely predetermined uniform distance from the respective said outer surface, a plurality of other slots each penetrating a respective said inner surface with its bottom intersecting the sidewalls of a respective dovetail slot, the width of each said other slot being not less than the bottom width of a respective dovetail slot; and a plurality of structural elements of uniform length joining said structural members, with each said structural element having a dovetail tongue at each end portion thereof closely fitting and received in a respective one of a said dovetail slot pair and having a shouldered portion bottomed in a respective said other slot.

2. A wooden building unit assembly having a dimension defined as the distance between first and second spaced parallel planes and comprising first and second plate members which exhibit unavoidable variances as to stock thickness between opposite surfaces thereof; said plate members being disposed in parallel relation with the outer surface of each lying in a respective said plane; a plurality of oppositely disposed pairs of key slots inside the inner surfaces of said plate members, each said key slot having side walls converging toward the respective said inner surface and a bottom wall, with each said bottom wall spaced a precisely predetermined uniform distance from the respective said outer surface, a plurality of other slots each penetrating a respective said inner surface with its bottom intersecting the sidewalls of a respective key slot, the width of each said other slot being not less than the bottom width of a respective key slot; and a plurality of stud elements of uniform length joining said plate members, with each said stud element having a tongue at each end portion thereof closely fitting and received in a respective one of said key slot pair and having a shouldered portion bottomed in a respective said other slot.

References Cited in the file of this patent UNITED STATES PATENTS 2,495,966 Haines Jan. 31, 1950 2,880,470 Pickersgill Apr. 7, 1959 2,902,733 Justus Sept. 8, 1959 

1. A STRUCTURAL ASSEMBLY HAVING A DIMENSION DEFINED AS THE DISTANCE BETWEEN FIRST AND SECOND SPACED PARALLEL PLANES AND COMPRISING FIRST AND SECOND STRUCTURAL MEMBERS WHICH EXHIBIT UNAVOIDABLE VARIANCES AS TO STOCK THICKNESS BETWEEN OPPOSITE SURFACES THEREOF; SAID MEMBERS BEING DISPOSED IN PARALLEL RELATION WITH THE OUTER SURFACE OF EACH LYING IN A RESPECTIVE SAID PLANE; A PLURALITY OF OPPOSITELY DISPOSED PAIRS OF DOVETAIL SLOTS INSIDE THE INNER SURFACES OF SAID STRUCTURAL MEMBERS, EACH SAID SLOT HAVING SIDE WALLS CONVERGING TOWARD THE RESPECTIVE SAID INNER SURFACE AND A BOTTOM WALL, WITH EACH SAID BOTTOM WALL SPACED A PRECISELY PREDETERMINED UNIFORM DISTANCE FROM THE RESPECTIVE SAID OUTER SURFACE, A PLURALITY OF OTHER SLOTS EACH PENETRATING A RESPECTIVE SAID INNER SURFACE WITH ITS BOTTOM INTERSECTING THE SIDEWALLS OF A RESPECTIVE DOVETAIL SLOT, THE WIDTH OF EACH SAID OTHER SLOT BEING NOT LESS THAN THE BOTTOM WIDTH OF A RESPECTIVE DOVETAIL SLOT; AND A PLURALITY OF STRUCTURAL ELEMENTS OF UNIFORM LENGTH JOINING SAID STRUCTURAL MEMBERS, WITH EACH SAID STRUCTURAL ELEMENT HAVING A DOVETAIL TONGUE AT EACH END PORTION THEREOF CLOSELY FITTING AND RECEIVED IN A RESPECTIVE ONE OF A SAID DOVETAIL SLOT PAIR AND HAVING A SHOULDERED PORTION BOTTOMED IN A RESPECTIVE SAID OTHER SLOT. 